We propose to assess the early development of bronchopulmonary infection and inflammation in infants with cystic fibrosis diagnosed through newborn screening. Infants will be studied propectively by means of bronchoalveolar lavage at diagnosis, 6, 12, 18, 24, 30, and 36 months of age to determine the time of initial appearance of airway disease and the relationship between markers of airways disease activity--Pseudomonas aeruginosa, neutrophils and neutrophil elastase.